I am currently working on the foundations of inference, and here especially on its proof-theoretic basis, pursuing a programme which I have called "proof-theoretic semantics". This programme builds on conceptual insights of general proof theory as initiated by Gerhard Gentzen in the 1930s and further developed by others since. Unlike most approaches in proof-theoretic semantics, which focus only on systems of formal logic, is my approach especially concerned with general reasoning systems based on inference rules for atomic sentences (which are also found in inductive definitions and in logic programs). My work in logical foundations also extends from the proof-theoretic framework towards a more interactive approach, as in dialogical or game-theoretics semantics. Besides, I am also interested in general philosophical questions related to logic and logical inference, the historical development of modern logic, and questions of cognitive science in relation to meaning, deduction and inference.